Old Lyme - On the banks of the Blackhall River near low tide, dozens of lifeless striped bass lie helter-skelter amid the mud and marsh grass, their metallic patterned sides still luminous.

"Some of them have their eyes and their guts pecked out," noted Maryann Nazarchyk of Niantic, who joined several other bird watchers at the Route 156 bridge over the river Wednesday to watch the feeding frenzy of sea gulls and other birds on the dead fish. "They're having a feast."

David Simpson, head of marine fisheries for the state Department of Energy and Environmental Protection, said several hundred young striped bass apparently died of "cold shock" after the single-digit temperatures and snowfall earlier this month. The fish kill appears to have been confined to the Blackhall River, a shallow tidal waterway that probably became clogged with ice and snow after the deep freeze, trapping the fish. Some of the dead fish have been carried by tides to the town-owned White Sands Beach and to the Great Island area, where several bald eagles have been spotted feeding on them.

"A lot of the striped bass just stay there (in the Blackhall) all winter," Simpson said. When the fish kill occurred, "there was a new moon, so there was little water in the river, and there was ice over it."

In larger rivers, striped bass can swim to deeper, warmer water when the temperature drops.

Several fishermen and others reported the fish kill to DEEP's marine headquarters in Old Lyme. After checking out the site, DEEP staff surmised the sudden cold was the culprit, Simpson said. The dead fish ranged from about 4 to 15 inches long, and all appeared to be in good health before they died, according to a DEEP report.

Simpson noted that a similar fish kill happened on the Blackhall after the blizzard last year.

"I don't believe it's a water quality issue," he said. "It's that the river is shallow, and they have limited ability to move out quickly when the temperature changes suddenly."

Some of the callers told DEEP they were concerned that the calcium chloride-magnesium chloride solution highway crews use to pretreat roads before snowstorms may have polluted the river and caused the fish kill, but Simpson said there would have been many more fish kills in other waterways if that were the case.

Patrick Abate, owner of River's End Tackle in Old Saybrook, saw the fish kill shortly after it happened about 10 days ago.

"I've been a striped bass fisherman all my life, and to see several hundred fish dead is a concern," he said.

While he's not discounting the explanation that the severe cold was the cause, he'd like the agency to study the phenomenon more thoroughly.

"Maybe they're right, but something of this magnitude, there should be a definitive answer," he said. "They should be doing an investigation and necropsy of the fish."

While anglers may lament the loss of so many of the popular game fish, bird watchers are appreciating the opportunities the phenomenon is giving them to pursue their hobby. Jim Denham of Essex brought his viewing scope to the bridge over the Blackhall Wednesday to note the different types of birds converging on the Blackhall marshes, many pecking at fish carcasses.

"There are black-backed gulls, black ducks, common mergansers, buffleheads, ring-billed gulls, herring gulls and two harriers," he said. "At Great Island, we saw eagles eating the fish. Eagles are scavengers."